Although somatic stem cells have been reported to exist in various adult organs, there have been few reports concerning stem cells in the heart. We here demonstrate that Sca-1-positive (Sca-1؉) cells in adult hearts have some of the features of stem cells. Sca-1؉ cells were isolated from adult murine hearts by a magnetic cell sorting system and cultured on gelatin-coated dishes. A fraction of Sca-1؉ cells stuck to the culture dish and proliferated slowly. When treated with oxytocin, Sca-1؉ cells expressed genes of cardiac transcription factors and contractile proteins and showed sarcomeric structure and spontaneous beating. Isoproterenol treatment increased the beating rate, which was accompanied by the intracellular Ca 2؉ transients. The cardiac Sca-1؉ cells expressed oxytocin receptor mRNA, and the expression was up-regulated after oxytocin treatment. Some of the Sca-1؉ cells expressed alkaline phosphatase after osteogenic induction and were stained with OilRed O after adipogenic induction. These results suggest that Sca-1؉ cells in the adult murine heart have potential as stem cells and may contribute to the regeneration of injured hearts.

Side population (SP) cells, which can be identified by their ability to exclude Hoechst 33342 dye, are one of the candidates for somatic stem cells. Although bone marrow SP cells are known to be long-term repopulating hematopoietic stem cells, there is little information about the characteristics of cardiac SP cells (CSPs). When cultured CSPs from neonatal rat hearts were treated with oxytocin or trichostatin A, some CSPs expressed cardiac-specific genes and proteins and showed spontaneous beating. When green fluorescent protein–positive CSPs were intravenously infused into adult rats, many more (∼12-fold) CSPs were migrated and homed in injured heart than in normal heart. CSPs in injured heart differentiated into cardiomyocytes, endothelial cells, or smooth muscle cells (4.4%, 6.7%, and 29% of total CSP-derived cells, respectively). These results suggest that CSPs are intrinsic cardiac stem cells and involved in the regeneration of diseased hearts.

Background-Angiotensin II (Ang II) has been reported to contribute to the pathogenesis of various human diseases including atherosclerosis, and inhibition of Ang II activity has been shown to reduce the morbidity and mortality of cardiovascular diseases. We have previously demonstrated that vascular cell senescence contributes to the pathogenesis of atherosclerosis; however, the effects of Ang II on vascular cell senescence have not been examined. Methods and Results-Ang

Abstract-The discovery of bone marrow-derived endothelial progenitors in the peripheral blood has promoted intensive studies on the potential of cell therapy for various human diseases. Accumulating evidence has suggested that implantation of bone marrow mononuclear cells effectively promotes neovascularization in ischemic tissues. It has also been reported that the implanted cells are incorporated not only into the newly formed vessels but also secrete angiogenic factors. However, the mechanism by which cell therapy improves tissue ischemia remains obscure. We enrolled 29 "no-option" patients with critical limb ischemia and treated ischemic limbs by implantation of peripheral mononuclear cells. Cell therapy using peripheral mononuclear cells was very effective for the treatment of limb ischemia, and its efficacy was associated with increases in the plasma levels of angiogenic factors, in particular interleukin-1␤ (IL-1␤). We then examined an experimental model of limb ischemia using IL-1␤-deficient mice. Implantation of IL-1␤-deficient mononuclear cells improved tissue ischemia as efficiently as that of wild-type cells. Both wild-type and IL-1␤-deficient mononuclear cells increased expression of IL-1␤ and thus induced angiogenic factors in muscle cells of ischemic limbs to a similar extent. In contrast, inability of muscle cells to secrete IL-1␤ markedly reduces induction of angiogenic factors and impairs neovascularization by cell implantation. Implanted cells do not secret angiogenic factors sufficient for neovascularization but, instead, stimulate muscle cells to produce angiogenic factors, thereby promoting neovascularization in ischemic tissues. Further studies will allow us to develop more effective treatments for ischemic vascular disease. Key Words: angiogenesis Ⅲ interleukins Ⅲ muscles P eripheral vascular disease (PVD), mainly caused by atherosclerosis, leads to obstruction of the blood supply to the lower or upper extremities. PVD is known to affect 10% to 15% of the adult population in developed countries and is often associated with coronary artery disease. 1 Arteriosclerosis obliterans (ASO) is the most common cause of PVD affecting the lower limbs. Peripheral ischemia can also result from various types of vasculitis, including thromboangiitis obliterans (TAO) or Buerger's disease, which affects small-and medium-sized arteries and is related to tobacco use and male sex but not to other coronary risk factors. The 2 cardinal symptoms of limb ischemia are intermittent claudication and rest pain: the latter symptom occurs in patients with critical limb ischemia and coincides with ischemic ulceration and gangrene. The treatments of PVD include pharmacotherapy, percutaneous transluminal angioplasty, and vascular surgery and are chosen depending on the severity of the symptoms and the arteries involved. 2 However, as many as 50% of patients with critical limb ischemia will undergo limb amputation within 1 year because of an insufficient response to the treatments. 1,2 Recent progress in understanding t...